Small cells have many applications, such as enabling 5G, powering DAS systems and providing location-based services, as Sam Fenwick reports

Small cells may be less familiar to the typical person on the street than their Wi-Fi access point counterparts, but vendors expect them to play a much bigger role in future, once 5G roll-outs take place.

Amit Jain, SpiderCloud Wireless’s VP of product management and marketing, says: “Most carriers believe that small cells will be almost essential for 5G. I don’t know how you would do a macrocell covering a few kilometres with millimetre wave (mmwave) – the propagation characteristics of that spectrum wouldn’t allow you to do that.” He expects that a lot of 5G deployments will use outdoor small cells and that indoor 5G small cells for enterprises will take longer to bring to market, “but will be an essential part of any 5G roll-out”.

Nick Johnson, ip.access’s CTO, is broadly in agreement. “There’s a laws of physics reason why small cells are imperative for mmwave and we’re at the early stages of our mmwave small cell story.” He notes that in terms of sub-6GHz 5G deployments, his company feels that it is in a good position as it can modify its 3.5GHz product “to make something that would be 5G New Radio-like, maybe with much wider channels, much wider bandwidth, much greater throughput”. That said, he believes the initial 5G deployments in the sub-6GHz band will be with macrocells.

In addition, “we’ll probably build a generation of outdoor small cells for fixed wireless access applications and then, when the handsets come along for smartphone applications for mmwave, we see quite a rich market in both sub-6GHz and mmwave for 5G small cells”.

One issue here is that of the challenges network operators will face when it comes to deploying outdoor small cells at the high densities 5G will require. Jain says: “There are efforts on the legislative side to get more ‘right of way’-style access for wireless operators. Just like when the electricity or telephone networks were being built, cities had to grant right of way to the utilities that were building them, otherwise none of these networks could have been built; similar approaches must be looked at for 5G. Without those, there will be no 5G network, we’ll be limited to LTE.”

Jonathan Freeman, Arqiva’s product and technology director, highlights the willingness of councils and supporting organisations to assist in the deployment of small cells in the UK and notes that it is something of a “learning exercise” given the need to consider logistical issues such as road closures, traffic management and 24/7 access. He cites the recent changes that have been made to the planning regime for small cell deployments and expects further enhancements.

Freeman says that access to ducts is crucial for small cell roll-out and believes it will also require access to dark fibre. This, in his view, creates a big role for Ofcom, given its efforts to improve access to Openreach’s infrastructure, and he says Arqiva is very much looking to Ofcom to make further progress on this front.

From a cost of ownership perspective, Freeman adds that Arqiva has done a lot of work to compensate for the fact that many small cells are deployed under busy roads, opting for a swap and replacement approach rather than one in which an engineer spends a lot of time trying to fix an issue in situ. This has involved a lot of work to deskill the process, so that small cells can be swapped out by road maintenance staff rather than telecoms engineers.

Art King, SpiderCloud Wireless’s director of enterprise services and technologies, says there is also “quite a lot of activity” under way with companies that own advertising street furniture, such as JCDecaux, and various suppliers to determine how they can be used to house low-powered small cells three to four metres above street level, thereby eliminating a lot of the issues around obtaining the necessary approvals and sites.

5G and Wi-Fi – friends or foes?Graham Payne, Opencell’s CEO, says when it comes to 5G, “there is a huge debate as to whether the small cells are going to be outdoors on lampposts and signs and so on or whether they’re going to be in-building. Most people now realise that the 5G small cells outside of buildings on lampposts and in signs aren’t going to penetrate into buildings because of the new glass being used and so they’re not going to add much value. Significantly better value will be achieved by putting 5G equipment inside buildings.”

However, when this happens, 5G will be entering Wi-Fi’s traditional domain. Payne doesn’t see this as an issue because, when it comes to voice, Wi-Fi calling lacks the cellular standards’ Quality of Service (QoS) control and their ability to prioritise voice over data, so that while it “can work pretty well” for residential users, “it’s just rubbish” in an office environment. On the data side, he believes that when it becomes available, people will want to use both 5G and Wi-Fi.

“We supply offices that have millions of pounds of investment in Wi-Fi and have invested more in Wi-Fi than in their mobile phone service. Even then, the Wi-Fi is so heavily used, it can be of variable quality.” While he expects Wi-Fi to improve as a standard, he doesn’t believe that it will be able to keep up with the demand for data, given the physical limits on the amount of data throughput that can be achieved for a given amount of spectrum (Shannon’s Law) and the interference issues that will occur when attempting to boost capacity by reducing cell sizes in an attempt to fit more Wi-Fi access points into the same building. He therefore sees 5G as a means of off-loading data traffic from Wi-Fi and expects this to result in a scenario in which devices don’t need cabled Ethernet connections any more.

Driving DAS with small cellsOne of the uses for small cells, that we covered in March last year, is using them to drive Distributed Antenna Systems (DAS) – an approach that cuts out the need to use expensive macro base stations and RF attenuators. Both ip.access and SpiderCloud are active in this area. Johnson says that ip.access has been working with a DAS provider to integrate its small cell technology with the DAS itself and is on the brink of two or three high-capacity deployments with the same partner. It has designed a system for a seafront location near a temple “where there are lots of festivals, and so for a few hours there might be 100,000 people gathered in a 200-300 square metre space and they’re all wanting to take selfies or pictures of the guru, so the demand on the network is huge”.

There has been larger-scale collaboration in the industry, with the purchase in July last year of SpiderCloud Wireless by Corning, a large DAS OEM, and CommScope’s acquisition of Airvana in October 2015.

SpiderCloud’s Jain highlights Verizon’s request to the five DAS vendors it uses to integrate their systems with SpiderCloud’s small cells. He notes that one of the big things that has made driving DAS with small cells possible is the big improvement in the number of simultaneous users each small cell can support.

“If you went back three to four years ago, a small cell could only support 16 or 32 simultaneous users, and then when you took that small cell and used it to drive a DAS that was covering, say, 100,000 sq ft, the small cell would not be able to serve the number of users that you had in that very large area.”

Modern small cells can serve up to 128 users and this improvement “has really made it feasible to drive DAS systems with small cells”. Jain adds that it is now typical for six to 12 of his company’s small cells to be placed in a shelf or rack and have this system used as a multiple-sector base station, with each ‘sector’ supporting 128 users. He believes there is no reason to try to push individual small cells’ capacity beyond 128 concurrent users given that they are sharing the same radio resources, making it better to up the number of small cells used for particularly large deployments.

Looking beyond exclusive spectrumJain adds that one of the most interesting innovations he is seeing in the small cell market is the introduction of a technology called LAA – licence-assisted access to unlicensed spectrum, which allows carriers to aggregate their spectrum with that in the 5GHz unlicensed band to provide more bandwidth to subscribers; it is a ‘polite protocol’ as it has listen-before-talk functionality to aid co-existence with other protocols that use unlicensed spectrum, such as Wi-Fi.

He adds that unlike Wi-Fi, LAA allows all the control channel messaging and real-time or high-priority traffic to occur over licensed spectrum. “It’s a ‘best of both worlds’ approach where you get the benefit of the licensed band where you need guaranteed availability of spectrum, while the unlicensed band allows you to double or triple the amount of bandwidth you can get.”

Jain adds that SpiderCloud has recently done some work with Sprint, a US MNO, which in some of its markets has only 5MHz of spectrum, which can only generate 20-30Mbps of peak throughput. “When they took that 5MHz of spectrum and combined it with 20MHz of unlicensed spectrum using LAA, they could see the peak rates more than quadruple to 120-130Mbps, providing carriers with tremendous leverage on the licensed spectrum holding that they have. It’s really valuable when used in-doors where unlicensed spectrum works best.”

He says that while SpiderCloud’s work with LAA is in the US, mobile operators in Europe are looking at LAA, with the majority having “at least talked about at least one trial or another”.

Johnson highlights one development “that’s really getting a head of steam” in the US: the Citizens Broadband Radio Service (CBRS), which consists of 150MHz in the 3.5GHz band, which the FCC is “licensing in a new, very exciting way”. It has a three-tiered scheme, which includes about 50MHz set aside for general access for equipment that works in conjunction with a software-based spectrum access client to allow dynamic spectrum sharing. The software queries a central database to determine which part of this spectrum it can use in any given location.

He adds that in the US, a lot of “existing fixed-access players who were deploying proprietary kit in [3.5GHz] are now getting ready to deploy LTE-based kit in 3.5GHz, the application being broadband access for remote communities. In the US, there’s a surprisingly big market for communities that are beyond the reach of wired infrastructure and so they currently rely on satellite or microwave, sometimes millimetre wave, and so there’s a lot of wireless internet service providers who are getting ready to deploy CBRS equipment for that application.”

Ip.access’s Viper solution, which can carry multiple service providers on a single RF carrier, also supports CBRS and “probably in a year you’ll start to see Samsung and Apple handsets that can cover the whole band”, but before then Johnson expects it to be used to provide enterprises with mobile broadband.

Beyond capacity and coverageSmall cells aren’t just about capacity and driving DAS – there is a raft of other applications they can enable. In last month’s issue, Johnson discussed how low-powered small cells can be used to provide retailers with aggregated data, which can then be used to fine-tune their in-store displays. Jain says SpiderCloud is active in this area and adds that small cells can also be used in “smart building applications where the number of devices connected to a small cell is used as a proxy for how many employees or customers are in part of a building, and we have a partner that looks at adjusting HVAC and heating depending on the number of users”.

He adds that SpiderCloud has also worked to allow the data transmitted in in-building small cell enterprise deployments to stay local and be integrated with the enterprise’s other IT systems, as opposed to going back to their carrier(s)’ networks. One use-case for this is in hospitals, where data on patients must stay within the premises and the use of LTE-connected tablets by staff has been suggested as a means of alleviating a traffic jam on Wi-Fi networks caused by patient/guest/employee devices that could block clinical devices. In this type of scenario, Jain explains that local data breakout for data traffic from these tablets is critical to stay compliant with regulations.

Small cells can be used to enable location-based services and to help smart buildings determine how many people are present and adjust heating and air conditioning accordingly

SpiderCloud has also enabled group-calling-style applications and Jain says small cells have a role to play in enabling location-based dispatch applications which, for example, in a large manufacturing complex can allow the closest technician with the required skills to be alerted to a malfunctioning machine and given all the information they need before they reach it, instead of having to send a page “over the entire campus and having people from all over the building trying to rush to that area or co-ordinate [with each other]”.

However, he adds that these kind of use-cases “are not straightforward to implement and require a fair amount of customisation” based on the user organisation’s needs.

From what we have heard, small cells are set to be increasingly ubiquitous. Given the extent to which 5G seems to be seen on the international stage as a future source of productivity, let’s hope that when the time comes to deploy small cells at scale, the regulatory and planning environment won’t be an issue.

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